1. Field of the Invention
This invention relates generally to audio amplifiers, and more particularly to a channel-to-channel separation technique to resolve cross coupling problems associated with multi-channel audio amplifier layouts.
2. Description of the Prior Art
Typical true digital audio amplifier (TDAA) systems include two demodulation inductors per audio channel. These demodulation inductors tend to couple in multi-channel boards if they are placed too close to one another; and this characteristic causes inferior channel-to-channel separation and other undesirable artifacts. This cross coupling is particularly problematic when downsizing printed circuit boards (PCBs), since inductors will be then be placed even closer to one another.
Two common techniques have been employed to resolve inductor coupling problems. One technique includes use of fully encapsulated demodulation inductors (in contrast to bar-type, high air-gap inductors). This technique, however, has negative affects on audio performance since it causes and increase in THD. Another technique includes use of large physical PCB spacing between audio channels. This technique is also problematic however, since it has a negative influence on total PCB size, i.e., the amplifier size/power ratio goes up.
In view of the foregoing, it would both desirable and advantageous to provide an inductor layout technique that minimizes or eliminates cross coupling between audio amplifier channels caused by demodulation inductors spacing. It would be further advantageous if the layout technique provided a way to further minimize printed circuit board sizes associated with multi-channel audio amplifiers such as TDAAs.
The present invention is directed to audio amplifier output stage layout techniques to achieve minimum cross coupling between audio amplifier channels. Regarding TDAA output stages, the typical TDAA includes two demodulation inductors per audio channel. The two pair of demodulation inductors associated with the TDAA are arranged to form an X-pattern to simultaneously minimize cross coupling between audio amplifier channels and reduce PCB layout size.
According to one aspect of the invention, an audio amplifier output stage layout technique is implemented to reduce the amplifier size/power ratio.
In yet another aspect of the invention, an audio amplifier output stage layout technique is implemented to improve audio performance, i.e. minimize channel-to-channel cross coupling.
In still another aspect of the invention, an audio amplifier output stage layout technique is implemented to improve EMI performance due to minimal capacitive and inductive coupling between PCB tracks.